This invention relates to a compressor, and more particularly, to a scroll type compressor for an air conditioning apparatus which includes a mechanism for adjusting the displacement of the compressor.
Scroll type fluid displacement apparatus are well known in the prior art. For example, U.S. Pat. No. 801,182 (Creux) discloses a device including two scrolls each having a circular end plate and a spiroidal or involute spiral element. These scrolls are maintained angularly and radially offset so that both spiral elements interfit to make a plurality of line contacts between their spiral curved surfaces to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scrolls shifts the line contact along the spiral curved surfaces and, as a result, the volume of the fluid pockets changes. Since the volume of the fluid pockets increases or decreases dependent on the direction of the orbital motion, the scroll type fluid apparatus is applicable to compress, expand or pump fluids.
Scroll type fluid displacement apparatus are suitable for use as refrigerant compressors in air conditioners. In such air conditioners, thermal control in the room or control of air conditioner is generally accomplished by intermittent operation of the compressor which in turn is activated or controlled by a signal from a thermostat located in the room being cooled. Once the temperature in the room has been cooled down to a desired temperature, the refrigerant capacity of the air conditioner for supplemental cooling because of further temperature changes in the room, or for keeping the room at the desired temperature, generally need not be very large. However, prior art air conditioners do not have capacity control mechanisms. Therefore, after the room has been cooled to the desired temperature, the manner for controlling the output of the compressor is by intermittent operation of the compressor. The relatively large load, which is required to drive the compressor, is thus intermittently applied to the driving source. When the compressor is used in an automotive air conditioner, it is driven by the engine of automobile through a electromagnetic clutch. Such prior art automotive air conditioners face the same output problem once the passenger compartment reaches a desired temperature. Control of the compressor's output is accomplished by intermittent operation of the compressor through a magnetic clutch which connects the automobile engine to the compressor. The relatively large load, which is required to drive the compressor, is thus intermittently applied to the automobile engine.